This invention relates to an electronic musical instrument having a plurality of musical tone forming systems capable of producing musical tones different in tone quality, and more particularly to a tone production control of the different types of the musical tone forming systems of the electronic musical instrument.
Various methods of forming musical tones in electronic musical instruments have been proposed. For instance, the following methods are well known in the art:
(1) A method in which out of a waveform memory in which a musical tone waveform of a predetermined tone color is stored, the musical tone waveform is repeatedly read to produce a musical tone.
(2) A method in which the relative amplitudes of various harmonic components are individually controlled, and thereafter mixed to produce a musical tone waveform signal having one desired tone color.
(3) A method in which a tone source waveform signal having a number of harmonic components is applied to a fixed type filter (formant filter) realizing a predetermined tone color, thereby to effect tone color formation.
(4) A method in which a tone source waveform signal having a number of harmonic components is applied to a voltage controlled type filter, thereby to effect intricate tone color formation.
It is true that each of the above-described conventional methods has its own superiority and merits. However, if these methods are separately applied to an electronic musical instrument, the performance of the musical instrument is biased, and accordingly it is impossible to provide an ideal electronic musical instrument. One of the ideal images for the electronic musical instrument resides in that the electronic musical instrument is so designed as to freely produces various musical tones different in tone quality, thereby to improve its performance ability as a musical instrument. For this purpose, it is desirable that a plurality of musical tone forming systems capable of individually producing musical tones different in tone quality according to different musical tone forming methods are incorporated in one and the same electronic musical instrument, and the musical tones formed by the various systems are simultaneously or selectively produced.
If an improved electronic musical instrument having the above-described plurality of musical tone forming systems is provided, then undoubtedly the electronic musical instrument will have a number of operating levers for controlling tone color, tone volume, tone pitch, etc. Accordingly, such an electronic musical instrument may suffer from the disadvantage that it is difficult for the performer to carry out the switching operations of the various control levers provided for the various musical tone forming systems. In other words, as the musical tone controls (the controls of tone color, tone volume, tone pitch, etc.) are carried out separately according to the various musical tone forming systems, there are provided a number of operating levers for each of the systems, and accordingly the number of operating levers as a whole is extremely increased. Therefore, for instance, when it is intended to change one musical tone forming system to another one during the performance, the performer must carry out a troublesome switching operation that after setting the operating levers of the musical tone forming system being employed to the off positions, he has to operate desired operating levers of a new musical tone forming system.